1. Field of the Invention
This invention relates to an alloy for a diesel engine valve which is excellent in the corrosion resistance and the strength, and a method for producing a diesel engine valve.
2. Description of the Prior Art
Heretofore, heat resisting steels such as JIS SUH 35(Fe-9Mn-21Cr-4Ni-0.5C-0.4N) or the like have been used as a material for inlet valves and exhaust valves of diesel engines, however Nimonic 80A (described later as conventional alloy No.7 in Table 1) which is a Ni-based supper heat resisting alloy containing 20% of Cr and more excellent in the corrosion resistance is beginning to be employed considering power up of the generating power and temperature rise of combusion gas of the diesel engines in recent years.
However, aforementioned Nimonic 80A is sufficiently excellent in the strength, although there is a problem in that it is not sufficient in the corrosion resistance, especially in resistance against sulfure attack caused by sulfides formed on the surface of the valves according to sulfur contained in fuel.
As compared with the above, although Udimet 520 (described later as conventional alloy No.8 in Table 1) which contains 12% of Co in addition to 20% of Cr has excellent corrosion resistance, there is a problem in the cost owing to addition of expensive Co in a large quantity.
Furthermore, Nimonic 81 (described later as conventional alloy No.9 in Table 1) of which Cr content is increased into 30% has sufficient corrosion resistance because of the addition of Cr in a large quantity, but there is another problem in that it is insufficient in the strength as inlet and exhaust valves of the diesel engines.